1. Field of the Invention
This invention relates to a profile gauge for measuring and indicating the diametric profile of a bone opening and is particularly, although not exclusively, applicable for use with an acetabular cup loading tube which is provided with a skirt.
2. Description of the Prior Art
In certain surgical operations it is convenient to be able to measure the diametric profile of a bone opening, for example, if a plate of specific size is to be used or if an acetabular cup is to be implanted into an acetabular socket.
U.S. Pat. No. 5,527,317 shows an apparatus for implanting an acetabular cup employing a loading tube adapted for alignment with an acetabular socket. The bore of the tube being dimensioned to receive an acetabular cup as a sliding fit to guide it into the socket and the present invention can provide a profile gauge which can be used with such a loading tube.
If a rim cutter is used to produce a step inside the bony rim of a natural acetabulum, two problems can arise. Firstly it demands a very high level of surgeon patience, care, calmness, experience, determination and skill to position the cutter accurately and hold it on course. Otherwise, the cutter can cut eccentrically and find its own orientation. Secondly, many acetabulae are insufficiently circular to allow the rim cutter to prepare a ledge around much more than about 180.degree. and this does not permit a loading tube to seat and seal.
Furthermore, where in revision surgery, bone chips are used to reform the acetabulum the rim cutter cannot cut the recess in a bed of loose morsels of bone. Sometimes a bone graft is contained in a surgeon formed metal mesh which in turn can be anchored by bone screws. With this arrangement a rim cutter must not be used to cut this metal mesh inside the patient.
In order to overcome the difficulties, the proposed solution for both non-circular and bone chip acetabular rims is to avoid the rim cutting operation and to trim the skirt of the loading tube so that it accurately fits the bony (or grafted) acetabular rim. Thus the skirt can be trimmed to fit either within the rim or around it.